Such belts have accurate geometrical shapes which satisfy standards, e.g. German standard DIN 7867 or draft international standard ISO R 15-506. They are used in particular in the automobile and household appliance industries (e.g. for driving a drum in a washing machine or a tumble drier) and they may include ribs having truncated tops, i.e. which are trapeziumshaped in cross-section.
After a certain amount of service, it is observed that belts of this type often suffer from cracking along the edges between the small bases and the sides of trapezium-section ribs. The cracking is due to stress concentrations on the edges by virtue of contact between the sides and the edges of the ribs against the corresponding surfaces of the pulleys over which the belt passes, and it gives rise to rapid destruction of or damage to the belt.
The object of the present invention is to avoid this drawback of prior art belts, and consequently to increase belt lifetime.